Silicon-On-Insulator (SOI) technology realizes lower power consumption and higher speed operation, compared to transistors formed in a bulk semiconductor layer. In SOI technology, the source, body, and drain regions of the transistor are insulated from the substrate, which reduces parasitic junction capacitances and eliminates latch-up. However, floating body effects can result when the body of each transistor is left unconnected. The floating body effect causes the transistor's body to “float” to a potential determined by the various leakage currents into the body. This varying body potential can cause adverse floating body effects such as, e.g., drain current “kink”-effect, lower breakdown voltage and lower drain output resistance, which is problematic for analog circuit applications.
In SOI Analog/Mixed/IO circuits, a body contact transistor can be used to eliminate the floating body effect in SOI technology. SOI transistors are formed in a silicon semiconductor layer (SOI) over a buried insulating layer. SOI transistors also include a body formed in the silicon semiconductor substrate and disposed beneath a gate region of the transistor. In a floating-body SOI FET, the body is not externally accessible. Body-contacted SOI transistors also include a body contact for connecting the body of the SOI transistor to a bias potential. For example, SOI transistors generally require connecting a p-type conductivity body, in the case of an n-channel MOSFET, or an n-type conductivity body, in the case of a p-channel MOSFET, to a bias potential.
One method of connecting the body of the SOI transistor to a bias potential is to provide an edge contact to the body using a T-shaped or H-shaped gate poly layout. However, T-shaped and H-shaped gate poly layouts add significant parasitic gate capacitance to the SOI transistor due to the portion of the poly layer not contributing to drive current of the transistor. Additionally, this type of body contact introduces a resistance between the external body contact and the internal body region, which limits the maximum frequency response of the body contact due to RC delay. The body contact also causes additional gate leakage because of the added polysilicon over gate dielectric. Also, as the SOI thickness is scaled down for high performance devices, increased body resistance may reduce the effectiveness of body contact.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.